Due to the high cost of traditional concrete components and the expensive transportation and labor costs associated therewith, there is a significant need in the construction industry to provide lightweight, precast, composite building panels that have superior strength and insulative properties. Previous attempts to provide these types of building panels have failed due to the expensive transportation costs and less than ideal insulative and thermal conductivity properties associated with prefabricated concrete wire-reinforced products. Further, due to the brittle nature of concrete, many of the previously used building panels are prone to cracks and other damage during transportation.
The relatively large weight per square foot of building panels of the prior art has resulted in high expenses arising not only from the amount of materials needed for fabrication, but also the cost of transporting and erecting the modules. Module weight also places effective limits on the height of structures, such as stacked modules e.g., due to load limitations of the building foundations, footings and/or lowermost modules. Furthermore, there is substantial fabrication labor expense that can arise from design, material, and labor costs associated with providing and placing reinforcement materials. Accordingly, it would be useful to provide a wall panel system for modular construction that is relatively light, can be readily stacked to increased heights and, preferably, inexpensive to design, manufacture, transport and erect.
In many situations panels or modules are situated in locations where it is desirable to have openings therethrough to accommodate doorways, windows, cables, pipes and the like. In some previous approaches, panels were required to be specially designed and cast so as to include any necessary openings, requiring careful planning and design, thus increasing costs due to the special, non-standard configuration of such panels. In other approaches, panels were cast without such openings and the openings were formed after casting, e.g. by sawing or similar procedures. Such post-casting procedures such as cutting, particularly through the thick and/or steel-reinforced panels as described above, is a relatively labor-intensive and expensive process. In many processes for creating openings, there is a relatively high potential for cracking or splitting of the panel or module. Accordingly, it would be useful to provide panels and modules wherein openings such as doors and windows may be integrated in desired locations with a reduced potential for cracking or splitting.
One other problem associated with metallic wire or bar materials used in conjunction with concrete is the varying rates of expansion and contraction. Thus, with extreme heating and cooling the embedded metallic materials tend to separate from the concrete, thus creating cracks which may lead to exposure to moisture and the eventual degradation of both the concrete and wire reinforcement due to corrosion.
One example of a composite building panel that attempts to resolve the aforementioned problems inherent in modular panel construction of the prior art is described in U.S. Pat. No. 6,202,375 to Kleinschmidt (the '375 patent), which is incorporated by reference in its entirety herein. In this invention, a building system is provided that utilizes an insulative core with an interior and exterior sheet of concrete and which is held together with a metallic wire mesh positioned on both sides of an insulative core. The wire mesh is embedded in concrete, and held together by a plurality of metallic wires extending through the insulative core at a right angle to the longitudinal plane of the insulative core and concrete panels. Although providing an advantage over homogenous concrete panels, the composite panel disclosed in the '375 patent does not provide the necessary strength and stiffness properties required during transportation and in high wind environments. Further, the metallic wire mesh materials are susceptible to corrosion when exposed to water during fabrication, and have poor insulative qualities due to the high heat transfer properties of metallic wire. Thus, the panels disclosed in the '375 patent may be more susceptible to failure when exposed to stresses during transportation, assembly or subsequent use.
In addition, attempts have been made to employ improved building materials that incorporate carbon fiber. For example, in U.S. Pat. No. 6,230,465 to Messenger, et al., which is incorporated herein in its entirety by reference, discloses concrete with a carbon fiber and steel reinforced precast frame. Unfortunately, the insulative properties of this invention are relatively poor due to the physical nature of the concrete and steel. Further, the excessive weight of the panels and inherent problems associated with transportation, stacking, etc. are present. Previously known prefabricated building panels have also not been found to have sufficient tensile and compressive strength when utilizing only concrete insulative foam materials or wire mesh. Thus, there is a significant need for a lightweight concrete building panel that has increased tensile and compressive strength, and which utilizes one or more commonly known building materials to achieve this purpose.
Furthermore, there is a need for a precast concrete foundation wall system that can be directly positioned on a prepared soil gravel or sand surface and interconnected to one or more foundation walls. After interconnection, a concrete floor can be poured which is operatively interconnected to the foundation walls and provides additional support.
Accordingly, there is a significant need in the construction and building industry to provide a composite building panel and foundation wall that may be used in modular construction and which is lightweight, provides superior strength and has high insulative values. Further, a method of making these types of building panels is needed that is inexpensive, utilizes commonly known manufacturing equipment, and which can be used to mass produce building panels for use in the modular construction of warehouses, low cost permanent housing, hotels, and other buildings. Finally there is a significant need for a precast foundation wall system that can be positioned on a prepared soil or gravel surface and operably interconnected to a poured concrete floor without utilizing onsite forms or other expensive building techniques.